executor: add concurrency limit on the union executor #16815
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If we do not limit the concurrency on the union executor, 'select * from t limit 1000' could make TiDB OOM on a large partition table.
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PTAL @XuHuaiyu |
lysu
reviewed
Sep 1, 2020
| @@ -1461,19 +1461,66 @@ func (e *UnionExec) Open(ctx context.Context) error { | |||
| return nil | |||
| } | |||
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@tiancaiamao maybe also need to make child.Open under flow-control...
some executors will buildCopRequest(make region cache or pd became busy) in "Open phase" 😭
github.com/pingcap/tidb/store/tikv.splitRanges(0xc003586178, 0xc00024bf80, 0xc0bb230bd0, 0xc003585f78, 0x100000000000000, 0xc4a1d6)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/store/tikv/coprocessor.go:295 +0x592
github.com/pingcap/tidb/store/tikv.buildCopTasks(0xc003586178, 0xc00024bf80, 0xc0bb230bd0, 0x23b0000, 0x1e70e80, 0xc038b15840, 0x240b760, 0xc0bb230ba0, 0x208
0)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/store/tikv/coprocessor.go:275 +0x114
github.com/pingcap/tidb/store/tikv.(*CopClient).Send(0xc0567eb1a0, 0x240b760, 0xc12e277cb0, 0xc0bba52a80, 0xc02d5a0b00, 0x10, 0x10)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/store/tikv/coprocessor.go:91 +0x205
github.com/pingcap/tidb/distsql.Select(0x240b760, 0xc12e277cb0, 0x2443e00, 0xc03eb2aa50, 0xc0bba52a80, 0xc01ba72100, 0x1f, 0x1f, 0xc01ba0f680, 0xc0035862f0, ...)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/distsql/distsql.go:44 +0x151
github.com/pingcap/tidb/distsql.SelectWithRuntimeStats(0x240b760, 0xc12e277cb0, 0x2443e00, 0xc03eb2aa50, 0xc0bba52a80, 0xc01ba72100, 0x1f, 0x1f, 0xc01ba0f680, 0xc05246ae00, ...)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/distsql/distsql.go:89 +0x97
github.com/pingcap/tidb/executor.selectResultHook.SelectResult(0x0, 0x240b760, 0xc12e277cb0, 0x2443e00, 0xc03eb2aa50, 0xc0bba52a80, 0xc01ba72100, 0x1f, 0x1f, 0xc01ba0f680, ...)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/executor/table_reader.go:48 +0x1c4
github.com/pingcap/tidb/executor.(*TableReaderExecutor).buildResp(0xc0283e6480, 0x240b760, 0xc12e277cb0, 0xc03d9ef018, 0x1, 0x1, 0x1, 0x0, 0x0, 0x0)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/executor/table_reader.go:187 +0x35d
github.com/pingcap/tidb/executor.(*TableReaderExecutor).Open(0xc0283e6480, 0x240b760, 0xc12e277cb0, 0x1f, 0x1f)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/executor/table_reader.go:120 +0x3cd
github.com/pingcap/tidb/executor.(*baseExecutor).Open(0xc01ba703c0, 0x240b760, 0xc12e277cb0, 0x0, 0x0)
/home/jenkins/agent/workspace/tidb_ghpr_build/go/src/github.com/pingcap/tidb/executor/executor.go:99 +0x7a
github.com/pingcap/tidb/executor.(*LimitExec).Open(0xc01ba703c0, 0x240b760, 0xc12e277cb0, 0x0, 0x0)
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close since #19827 |
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No release note, Please follow https://github.com/pingcap/community/blob/master/contributors/release-note-checker.md |
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What problem does this PR solve?
If we do not limit the concurrency of the union executor,
'select * from t limit 1000' could make TiDB OOM on a large partition table.
Problem Summary:
TiDB v3.0.3, on a large partition table
The union calls
Closebut the underlying childen node still running:For each partition, the union executor use a new goroutine.
The table reader has load too much data before the limit could take effect.
What is changed and how it works?
What's Changed:
How it Works:
Set a concurrency limiter for the union executor.
Do not spawn all goroutine immediately.
Related changes
Check List
Tests
The concurrency case is not easy to test, in this commit there is a simple test that just cover the new code.
Side effects
Maybe, because of the introduce of the concurrency limit.
Release note